#!/usr/bin/python3

"""
This helper script is able to extract a date and time from the name of all files in a directory and set their respective UNIX mtime (the modified timestamp).
Copyright (C) 2024  Benjamin Burkhardt

This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program.  If not, see <https://www.gnu.org/licenses/>.
"""

"""
Useful links:
- https://docs.python.org/3/library/datetime.html#strftime-and-strptime-behavior
- https://www.datacamp.com/tutorial/converting-strings-datetime-objects
- https://scrapfly.io/blog/parsing-datetime-strings-with-python-and-dateparser/
- https://stackoverflow.com/questions/466345/convert-string-jun-1-2005-133pm-into-datetime
"""


from datetime import datetime
from argparse import ArgumentParser, RawTextHelpFormatter
import os
import sys


class COLORS:
    HEADER = '\033[95m'
    OKBLUE = '\033[94m'
    OKCYAN = '\033[96m'
    OKGREEN = '\033[92m'
    WARNING = '\033[93m'
    FAIL = '\033[91m'
    ENDC = '\033[0m'
    BOLD = '\033[1m'
    UNDERLINE = '\033[4m'

class LOGGER:
    def __init__(self, verbose: bool = False):
        self.verbose = verbose

    def log(self,  to_log, verbose=False, end="\n"):
        to_log = to_log + COLORS.ENDC
        if (self.verbose and verbose) or not verbose:  # only print if it's not verbose or verbose is enabled
            print(to_log, end=end)


# set up the ArgumentParser for the CLI
parser = ArgumentParser(
    description='filename2mtime.py  Copyright (C) 2024  Benjamin Burkhardt\r\n'
                'This program comes with ABSOLUTELY NO WARRANTY and is licensed under the '
                'GNU General Public License 3.\r\n'
                'You should have received a copy of the GNU General Public License\r\n'
                'along with this program. If not, see <https://www.gnu.org/licenses/>.\r\n'
                '\r\n'
                'This helper script is able to extract a date and time from the name of all \r\n'
                'files in a directory and set their respective UNIX mtime (the modified timestamp).\r\n'
                'BE AWARE THAT ALL CHANGES TO THE FILES CANNOT BE UNDONE! USE AT YOUR OWN RISK!',
    epilog='by Benjamin Burkhardt, 2024',
    add_help=False,
    formatter_class=RawTextHelpFormatter)


parser.add_argument('-f', '--format', type=str, default="", help="give the format of the strings\r\nsee https://docs.python.org/3/library/datetime.html#strftime-and-strptime-behavior for more details")
parser.add_argument('-e', '--format-error-exit', action='store_true', default=False, help='exit if the format does not fit to one file')  # on/off flag
parser.add_argument('-v', '--verbose', action='store_true', default=False, help='enable verbose output')  # on/off flag
parser.add_argument('-h', '--help', action='store_true', default=False, help='display this help message and exit')  # on/off flag


# parse given arguments
args = parser.parse_args()

# print help and exit if prompted to
if args.help or not len(sys.argv) > 1:
    parser.print_help()
    exit(0)

# set up logger
logger = LOGGER(args.verbose)

# check for an empty format
if args.format == '' and not args.auto_format:
    logger.log(COLORS.FAIL + 'You need to specify a format.')
    parser.print_usage()
    exit(1)



# Start of the real program, format is surely set

all_files = os.listdir()
parsed_datetimes = {}
longest_filename_len = max([len(f) for f in all_files])


for f in all_files:
    try:
        parsed_datetimes[f] = datetime.strptime(f, args.format)
        logger.log(f"Detecting: {f} -> {parsed_datetimes[f]}", verbose=True)
    except ValueError:
        if args.format_error_exit:
            logger.log(f"{COLORS.WARNING}{f.ljust(longest_filename_len + 1)}: Failed to parse the date and time.")
            logger.log(f"{COLORS.FAIL}EXITING (as -e flag was set)!")
            exit(1)
        else:
            logger.log(f"{f.ljust(longest_filename_len + 1)}: {COLORS.WARNING}Failed to parse the date and time.")

for f, dt in parsed_datetimes.items():
    # get atime timestamp (as os.utime requires this as an argument - we leave it unchanged)
    atime_timestamp = os.stat(f).st_atime

    # get the mtime timestamp from the respective datetime object
    mtime_timestamp = dt.timestamp()

    # set the new mtime (atime stays unchanged)
    os.utime(f, (atime_timestamp, mtime_timestamp))